1 files changed, 100 insertions, 0 deletions
diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
new file mode 100755
index 000000000..fd1ffaa5a
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Alternate sleeping and spinning on randomly selected CPUs.  The purpose
+# of this script is to inflict random OS jitter on a concurrently running
+# test.
+#
+# Usage: jitter.sh me jittering-path duration [ sleepmax [ spinmax ] ]
+#
+# me: Random-number-generator seed salt.
+# duration: Time to run in seconds.
+# jittering-path: Path to file whose removal will stop this script.
+# sleepmax: Maximum microseconds to sleep, defaults to one second.
+# spinmax: Maximum microseconds to spin, defaults to one millisecond.
+#
+# Copyright (C) IBM Corporation, 2016
+#
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
+
+me=$(($1 * 1000))
+jittering=$2
+duration=$3
+sleepmax=${4-1000000}
+spinmax=${5-1000}
+
+n=1
+
+starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
+
+nohotplugcpus=
+for i in /sys/devices/system/cpu/cpu[0-9]*
+do
+	if test -f $i/online
+	then
+		:
+	else
+		curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
+		nohotplugcpus="$nohotplugcpus $curcpu"
+	fi
+done
+
+while :
+do
+	# Check for done.
+	t=`gawk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
+	if test "$t" -gt "$duration"
+	then
+		exit 0;
+	fi
+
+	# Check for stop request.
+	if ! test -f "$jittering"
+	then
+		exit 1;
+	fi
+
+	# Set affinity to randomly selected online CPU
+	if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
+		 sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
+	then
+		:
+	else
+		cpus=
+	fi
+	# Do not leave out non-hot-pluggable CPUs
+	cpus="$cpus $nohotplugcpus"
+
+	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
+		srand(n + me + systime());
+		ncpus = split(cpus, ca);
+		print ca[int(rand() * ncpus + 1)];
+	}' < /dev/null`
+	n=$(($n+1))
+	if ! taskset -c -p $cpumask $$ > /dev/null 2>&1
+	then
+		echo taskset failure: '"taskset -c -p ' $cpumask $$ '"'
+		exit 1
+	fi
+
+	# Sleep a random duration
+	sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
+		srand(n + me + systime());
+		printf("%06d", int(rand() * sleepmax));
+	}' < /dev/null`
+	n=$(($n+1))
+	sleep .$sleeptime
+
+	# Spin a random duration
+	limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
+		srand(n + me + systime());
+		printf("%06d", int(rand() * spinmax));
+	}' < /dev/null`
+	n=$(($n+1))
+	for i in {1..$limit}
+	do
+		echo > /dev/null
+	done
+done
+
+exit 1